This invention relates to hammer-type impact printers and, more particularly, to automatic typewriters and the like which rely on hammer-type impact printing mechanisms.
Hammer-type impact printing mechanisms are commonly found in computer printers where printing speed, rather than print quality, is the predominant concern. However, they may be advantageously utilized in high quality (e.g., typewriter quality) printers, as evidenced by the Xerox 800 Electronic Typing System, provided that suitable provision is made for enhancing the print quality.
One of the more difficult patterns for a hammer-type impact printer to produce is a straight, uniformly dense, multi-character line, such as a word or line length underscore. Typically, such a printer suffers from some "play" in the character and/or carriage positioning. Also, the inked ribbon or tape presented for underscoring purposes often includes both virgin and used stock. Thus, a multi-character tends to appear as a wavy, variably shaded line. That is, of course, aesthetically objectionable in automatic typewriters and the like which must satisfy high print quality standards.